1. Field of the Invention
This invention is related to the field of tube bending and more particularly to a bender that may make various types of bends including ninety degree bends in electrical conduit.
2. Description of the Related Art
Electrical conduit is widely used in the construction industry to provide mechanical protection to electrical wires. Electrical conduit is generally metallic tubing that has an inner diameter and an outer diameter and serves to house electrical wiring. Various forms of electrical conduit include electrical metallic tubing (EMT), intermediate metallic tubing (IMC), and galvanized rigid conduit (GRC). Typically, electrical conduit is installed at a job site prior to pulling the installed wiring through the conduit. As wiring may take on complicated paths to avoid obstructions in a structure, electrical conduit often needs to be bent to correspond to these wiring routes.
Although electrical conduit may be bent into a variety of configurations, the construction industry has adopted several common bend configurations which include offset bends, saddle bends, kick bends, and ninety degree bends. An offset bend comprises two equal and opposite bends in a straight length of conduit so that the two ends of the conduit are parallel but are offset a given perpendicular distance. An extension to the offset bend, the saddle bend consists of two complementary offset bends. The saddle bend therefore comprises two bends which are equal and opposite to another two bends. The kick bend, most likely the simplest bend to execute, consists of one bend such that the first end of the conduit is oriented to the second end of the conduit at an angle substantially forty-five degrees. Finally, the ninety degree bend is the most widely used conduit bend. As this terminology implies, a ninety degree bend comprises a bend such that the first end of the conduit is oriented to the second end of the conduit at a substantially ninety degree angle.
To achieve the above bend configurations, the construction industry uses several conduit bending techniques. All of these bending techniques can be broadly grouped into hand benders, power benders, and mechanical benders.
Hand benders are the oldest bending technique in art of conduit bending. Hand benders generally comprise a curved bending shoe for receiving and holding the conduit and leverage means for forming the bend. Even though hand benders are still currently used in the field of tube bending because they are inexpensive and portable, hand benders have significant disadvantages. Since hand benders are only designed to make one bend at a time, bending configurations that include more than one bend are difficult to implement. For example, a tradesmen making an offset bend using a hand bender makes the first bend and then must reposition the hand bender before making the second bend. This repositioning of the hand bender prior to making the second bend leads to highly variable and often inaccurate results. Highly variable results also occur in bend configurations involving one bend because the user force applied to bend the conduit is variable. An additional disadvantage of hand benders is that they are unable to effectively bend larger size conduit. Recent advances in hand benders include improved methods for receiving and holding the conduit in a bending shoe and measurement indicators. Measurement indicators aide a tradesmen in effectively repositioning the hand bender before making a second bend in a bend configuration.
Power benders are large pieces of equipment that typically relay on hydraulics or pneumatics to actuate bending shoes to produce bends in conduit. Power benders are currently adapted to produce offset bends, saddle bends, kick bends, and ninety degree bends. Given that the actuation of the bending shoes is automated, power benders produce highly accurate results. Additionally, the automation and the size of power benders provides for bending of larger sized conduit compared to hand benders. Even though the automation and the size of power benders provide several benefits to the art of conduit bending, this automation and this size makes power benders very expensive and immobile.
Mechanical benders seek to provide the benefits of both hand benders and power benders. Mechanical benders usually consist of bending shoes connected to a light weight bending frame. The bending shoes are generally actuated by a user but the mechanical bender may use gearing or leverage to provide mechanical advantage. Mechanical benders may alternatively be actuated by small electric motors. Several mechanical benders currently exist in the art of conduit bending. U.S. Pat. No. 5,222,384 Evans discloses a reciprocal conduit bender which may make equal and opposite simultaneous bends in a conduit. In addition to making generally accurate bends, mechanical benders are relatively less expensive than power benders, and are typically mobile and consequently may be easily used on construction sites; however, Evans and other mechanical benders have only been adapted to produce offset bends, saddle bends, and kick bends. Since the ninety degree bend is the most widely used bending configuration, the inability of mechanical benders to make ninety degree bends is a severe disadvantage.
Accordingly, what is needed in the art is a conduit bender that provides the advantages of the state of the art mechanical benders and is adapted to make ninety degree bends in electrical conduit. This bender should be generally mobile and should make accurate ninety degree bends in conduit while still being adapted to make accurate offset bends, saddle bends, and kick bends.